In the corrugated board industry, corrugated board is manufactured by adhering a corrugated, or fluted, sheet of paper to one or more flat sheets. A fluted sheet is referred to as a "medium", and a flat sheet is referred to as a "liner". A corrugated board consisting of a medium adhered to a single liner is referred to as "single ply corrugated board", "single ply board", or simply "single ply". By applying an additional liner to the other side of a medium, "double ply corrugated board", "double ply board", or "double ply" is formed. Single ply board is often used in packing fragile objects such as china and glass. Double ply board is often used in creating packaging products such as corrugated boxes and cases.
A fluted sheet is generally formed on a corrugating roll machine. The corrugating roll machine includes in series an upper corrugating roll, a lower corrugating roll, and a pressure roll, respectively, set to engage one another such that a medium can travel in a serpentine path therebetween. An example of such a system is set forth in FIG. 1. In operation of a corrugating roll machine, the upper corrugating roll 11 (FIG. 1) and the pressure roll 20 (FIG. 1) rotate in a clockwise direction, and the lower corrugating roll 12 (FIG. 1) rotates counterclockwise to move the medium 50 (FIG. 1) from the left side of FIG. 1 to the right.
The upper and lower corrugating rolls 11 and 12 are cylindrical and include multiple, elongate, sinusoidal protrusions 14 extending radially from the axis of rotation and along the length of the corrugating rolls. These protrusions are referred to as "flutes". A medium is formed by passing a flat sheet between the intermeshing flutes on the upper corrugating roll 11 and lower corrugating roll 12. As the sheet 50 passes over the flutes on the surfaces of the intermeshed corrugating rolls, the sheet conforms to the shape of the flutes. Steam and heat are introduced to accelerate the fluting process.
After the medium passes through the two intermeshing corrugating rolls, it continues to remain pressed against the flutes of the lower corrugating roll 12. As the medium travels around the path of the lower corrugating roll, the outer surface of the medium contacts a glue roll 22 (FIG. 1). The glue roll has adhesive on its surface so that it may apply adhesive to the contacting surface of the medium. The medium continues to travel along the outside of the lower corrugating roll to the pressure roll, where a liner 52 is inserted between the outer, glue-coated side of the medium and the pressure roll. The pressure applied by the pressure roll causes the medium to adhere to the liner so that a single ply board is formed.
In the process of manufacturing the single ply board, it is critical that the flutes of the medium are spaced evenly along the liner so that they adhere to the liner in a consistent manner. In order for this formation to be consistently accomplished, the medium must remain firmly against the flutes of the lower corrugating roll while the liner is being glued to the medium. However, once the medium is fluted, it has a tendency to return to a flattened state and pull away from the lower corrugating roll. If the medium is permitted to release from the lower corrugating roll, the flutes of the medium may become misaligned at the point the medium contacts the liner and the pressure roll. Thus, the medium must be held against the surface of the lower corrugating roll to ensure proper application of the adhesive and to prevent the flutes from overlapping or flattening out when they adhere to the liner at the pressure roll.
A series of guide elements 30, called "corrugating guide fingers", are used to keep the medium in contact with the lower corrugating roll. These corrugating guide fingers are mounted against the lower corrugating roll from a point adjacent to the upper corrugating roll to a location near the pressure roll. To maintain maximum contact between the medium and the lower corrugating roll, it is desirable to have the corrugating guide fingers contact the medium for as much of the distance as possible. The majority of problems occur at the juncture of the lower corrugating roll 12 and the pressure roll 20, hereinafter referred to as the "nip". The main problem that occurs at the nip is the corrugating guide finger does not extend far enough into the nip to maintain the medium against the lower corrugating roll until the medium reaches the contact point with the liner. At any location where the finger is not in contact with the medium prior to the juncture with the pressure roll, there is a possibility that the medium will pull away from the lower corrugating roll. If the medium separates from the lower corrugating roll, the flutes of the medium can overlap or bunch before the medium contacts the liner, which could cause the pressure roll to jam and shut down the entire corrugating process.
At present, corrugating guide fingers are substantially arc-shaped to follow the curve of the corrugating roll. Existing corrugating guide fingers have an outer arcuate surface and an inner arcuate surface. The inner arcuate surface has a radius that is slightly greater than the radius of the corrugating roll. The corrugating guide fingers define a leading end at the upstream, or upper corrugating roll, side of the lower corrugating roll, and a trailing end at the downstream, or pressure roll, side. The leading end is typically rounded and designed to pull the fluted medium away from the intermeshing flutes of the upper corrugating roll 11. The trailing end is designed to hold the medium in contact with the lower corrugating roll 12 before the medium adheres to the liner.
The trailing edge of existing corrugating guide fingers includes a linear surface joining the outer and inner arcuate surfaces. This surface creates a tangential point of contact between the finger and the pressure roll, and limits the amount the finger may be inserted into the nip. In addition, the tip of existing corrugating guide finger trailing ends are often blunt and squared-off, resulting in a tip which measures approximately one eighth to one sixteenth of an inch in width. This dimension is significant in that it does not permit the trailing edge to approach the nip, resulting in a gap where the medium is not supported before being attached to the liner. This gap results in a loss of contact with approximately one flute of the medium just prior to the contact of the liner with the medium. This, in turn, results in poor quality of corrugation and ultimately, a poor quality product.
Because corrugating guide fingers must stay in position against the medium, the corrugating guide fingers must be properly mounted relative to the lower corrugating roll. The preferred spacing between the inner surface of the corrugating guide finger and the outer surface of the lower corrugating roll is equal to the thickness of the medium. It is preferred that this spacing be consistent along the entire length of the corrugating guide finger. The spacing is hard to achieve because the medium is not in place when the fingers are installed. In addition, the exact spacing is difficult to achieve due to the confined space in which machinists are able to work to mount the corrugating guide fingers. Often, the corrugating guide fingers are spaced relative to the corrugating roll by visual inspection alone. This method of spacing is extremely arbitrary and usually results in an inappropriate gap between at least one portion of the corrugating guide finger and the lower corrugating roll.
If a portion of a finger is positioned too closely to the corrugating roll surface, there may be insufficient room for the medium to travel, which may cause the medium to catch and rip. This results in a shut down of the equipment which halts the entire manufacturing process.
If a portion of a finger is mounted too far away from the surface of the lower corrugating roll, the finger may allow too much play in the travel of the medium, which may cause the medium to move away from the lower corrugating roll or glue roll. This free travel may result in insufficient or excessive application of adhesive or bunching of the flutes of the medium before the medium reaches the nip, and ultimately may result in a poor quality product.
Thus, there is a need for a device that properly spaces a corrugating guide finger from a corrugating roll so that the corrugating guide finger may be fixed the correct distance from the corrugating roll.
There is a further need for a device that spaces a corrugating guide finger consistently and accurately along the corrugating guide finger's length relative to a corrugating roll to prevent tearing of the medium or creation of a poor quality product.
There is still a further need for a method of spacing a corrugating guide finger relative to a corrugating roll.
There is yet a further need for a method of spacing a corrugating guide finger consistently and accurately relative to a corrugating roll to prevent tearing of the medium or creation of poor quality product.